High temperature resistant vitreous inorganic fiber

ABSTRACT

A temperature resistant vitreous inorganic fiber having a use temperature of up to at least 1000° C., or greater, having after service mechanical integrity, is non-durable (soluble) in physiological fluids, and is produced from a melt containing silica, magnesia, a lanthanide series element-containing compound, and optionally zirconia.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of the filing date under 35 U.S.C.§119(e) of U.S. Provisional Application No. 60/483,169 filed Jun. 27,2003, which is hereby incorporated by reference.

BACKGROUND

A high temperature resistant vitreous fiber, useful as a heat or soundinsulating material is provided, which has a use temperature at least upto 1000° C. The high temperature resistant fiber is easilymanufacturable, exhibits low shrinkage, retains good mechanical strengthafter exposure to the service temperature, and is non-durable inphysiological fluids.

The insulation material industry has determined that it is desirable toutilize fibers in heat and sound insulating applications which are notdurable in physiological fluids, such as lung fluid. While candidatematerials have been proposed, the use temperature limit of thesematerials have not been high enough to accommodate many of theapplications to which high temperature resistant fibers, includingrefractory glass and ceramic fibers, are applied. In particular, hightemperature resistant fibers should exhibit minimal linear shrinkage atexpected exposure temperatures, in order to provide effective thermalprotection to the article being insulated.

Many compositions within the man-made vitreous fiber family of materialshave been proposed, which are decomposable in a physiological medium.These glass fibers generally have a significant alkali metal oxidecontent, which often results in a low use temperature limit.

Canadian Patent Application No. 2017344 describes a glass fiber havingphysiological solubility formed from glasses containing as requiredcomponents silica, calcia and Na₂O, as preferred components, magnesiaand K₂O, and as optional components boria, alumina, titania, ironoxides, and fluoride.

International Publication No. WO 90/02713 describes mineral fibers whichare soluble in saline solutions, the fibers having a compositionincluding silica, alumina, iron oxide, calcia, magnesia, Na₂O and K₂O.

U.S. Pat. No. 5,108,957 describes glass compositions useful for formingfibers which are able to be degraded in a physiological mediumcontaining as required components silica, calcia, Na₂O plus K₂O, andboria, and optionally alumina, magnesia, fluoride and P₂O₅. It describesthe presence of phosphorus as having the effect of increasing the rateof decomposition of the fibers in a physiological medium.

Other patents which cite the effect of phosphorus in favoring biologicalsolubility of mineral fibers include International Publication No. WO92/09536, describing mineral fibers containing substantially silica andcalcia, but optionally magnesia and Na₂O plus K₂O, in which the presenceof phosphorus oxide decreases the stabilizing effect of aluminum andiron on the glass matrix. These fibers are typically produced at lowertemperatures than refractory ceramic fibers. We have observed that atmelt temperatures required for high temperature resistant fibers(1700-2000° C.), phosphorus oxide at levels as low as a few percent cancause severe degradation and/or erosion of furnace components.

Canadian Patent Application No. 2043699 describes fibers which decomposein the presence of a physiological medium, which contain silica,alumina, calcia, magnesia, P₂O₅, optionally iron oxide, and Na₂O plusK₂O.

French Patent Application No. 2662687 describes mineral fibers whichdecompose in the presence of a physiological medium, which containsilica, alumina, calcia, magnesia, P₂O₅, iron oxide and Na₂O plus K₂Oplus TiO₂.

U.S. Pat. No. 4,604,097 describes a bioabsorbable glass fiber comprisinggenerally a binary mixture of calcia and phosphorous pentoxide, buthaving other constituents such as calcium fluoride, water, and one ormore oxides such as magnesia, zinc oxide, strontium oxide, sodium oxide,potassium oxide, lithium oxide or aluminum oxide.

International Publication No. WO 92/07801 describes a bioabsorbableglass fiber comprising phosphorous pentoxide, and iron oxide. A portionof the P₂O₅ may be replaced by silica, and a portion of the iron oxidemay be replaced by alumina. Optionally, the fiber contains a divalentcation compound selected from Ca, Zn and/or Mg, and an alkali metalcation compound selected from Na, K, and/or Li.

U.S. Pat. No. 5,055,428 describes a soda lime aluminoboro-silicate glassfiber composition which is soluble in a synthetic lung solution. Aluminacontent is decreased with an increase in boria, and an adjustment insilica, calcia, magnesia, K₂O and optionally Na₂O. Other components mayinclude iron oxide, titania, fluorine, barium oxide and zinc oxide.

International Publication No. WO 87/05007 describes an inorganic fiberhaving solubility in saline solution and including silica, calcia,magnesia, and optionally alumina. International Publication No. WO89/12032 describes an inorganic fiber having extractable silicon inphysiological saline solution and including silica, calcia, optionallymagnesia, alkali metal oxides, and one or more of alumina, zirconia,titania, boria and iron oxides.

International Publication No. WO 93/15028 describes vitreous fibers thatare saline soluble which in one usage crystallize to diopside uponexposure to 1000° C. and/or 800° C. for 24 hours and have thecomposition described in weight percent of silica 59-64, alumina 0-3.5,calcia 19-23 and magnesia 14-17, and which in another usage crystallizeto wollastonite/pseudowollastonite and have the composition described inweight percent of silica 60-67, alumina 0-3.5, calcia 26-35 and magnesia4-6.

International Publication No. WO 03/059835 discloses a calcium-silicatefiber containing 1.3-1.5 weight percent La₂O_(3.)

The fibers described in the above identified patent publications arelimited, however, in their use temperature, and are therefore unsuitablefor high temperature insulation applications, such as furnace liningsfor use above 1000° C., and reinforcement applications such as metalmatrix composites and friction applications.

U.S. Pat. Nos. 6,030,910, 6,025,288 and 5,874,375, to UnifraxCorporation, the assignee of the present application, discloseparticular inorganic fibers comprising the products of a substantiallysilica and magnesia fiberizable melt, that are soluble in physiologicalfluid and have good shrinkage and mechanical characteristics at a highuse temperature limit.

A product based on non-durable fiber chemistry is marketed by UnifraxCorporation (Niagara Falls, N.Y.) under the trademark INSULFRAX, havingthe nominal weight percent composition of 65% SiO₂, 31.1% CaO, 3.2% MgO,0.3% Al₂O₃ and 0.3% Fe₂O₃. Another product is sold by Thermal Ceramics(located in Augusta, Ga.) under the trademark SUPERWOOL, and is composedof 58.5% SiO₂, 35.4% CaO, 4.1% MgO and 0.7% Al₂O₃ by weight. Thismaterial has a use limit of 1000° C. and melts at approximately 1280°C., which is too low to be desirable for the high temperature insulationpurposes described above.

International Application No. WO 94/15883 discloses CaO/MgO/SiO₂ fiberswith additional constituents Al₂O₃, ZrO₂, and TiO₂, for which salinesolubility and refractoriness were investigated. That document statesthat saline solubility appeared to increase with increasing amounts ofMgO, whereas ZrO₂ and Al₂O₃ were detrimental to solubility. The presenceof TiO₂ (0.71-0.74 mol %) and Al₂O₃ (0.51-0.55 mol %) led to the fibersfailing the shrinkage criterion of 3.5% or less at 1260° C.

The document further states that fibers that are too high in SiO₂ aredifficult or impossible to form, and cites samples having 70.04, 73.28and 78.07% SiO₂ as examples which could not be fiberized.

U.S. Pat. Nos. 5,332,699, 5,421,714, 5,994,247, and 6,180,546 aredirected to high temperature resistant, soluble inorganic fibers.

In addition to temperature resistance as expressed by shrinkagecharacteristics that are important in fibers that are used ininsulation, it is also required that the fibers have mechanical strengthcharacteristics during and following exposure to the use or servicetemperature, that will permit the fiber to maintain its structuralintegrity and insulating characteristics in use.

One characteristic of the mechanical integrity of a fiber is its afterservice friability. The more friable a fiber, that is, the more easilyit is crushed or crumbled to a powder, the less mechanical integrity itpossesses. It has been observed that, in general, refractory fibers thatexhibit both high temperature resistance and non-durability inphysiological fluids also exhibit a high degree of after servicefriability. This results in the fiber's lacking the strength ormechanical integrity after exposure to the service temperature to beable to provide the necessary structure to accomplish its insulatingpurpose.

We have found high temperature resistant, non-durable fibers which doexhibit good mechanical integrity up to the service temperature. Othermeasures of mechanical integrity of fibers include compression strengthand compression recovery.

Refractory glass compositions which may exhibit target durability,shrinkage at temperature, and strength characteristics may not, however,be susceptible to fiberization, either by spinning or blowing from amelt of its components.

It is therefore desirable to provide high temperature resistantrefractory glass fiber, that is readily manufacturable from a melthaving a viscosity suitable for blowing or spinning fiber, and which isnon-durable in physiological fluids.

It is also desirable to provide high temperature resistant refractoryglass fiber, which is non-durable in physiological fluids, and whichexhibits good mechanical strength up to the service temperature.

It is further desirable to provide a high temperature resistantrefractory glass fiber, which is non-durable in physiological fluids,and which exhibits low shrinkage at the use temperature.

SUMMARY

High temperature resistant refractory vitreous inorganic fibers areprovided which are non-durable in physiological fluids. The fibers aremore soluble in simulated lung fluid than standard aluminosilicaterefractory ceramic fibers, and exhibit a temperature use limit up to atleast 1000° C. or greater. These fibers retain mechanical strength afterexposure to service temperatures. The fibers meeting the requirements ofbeing fiberizable, high temperature resistant, and non-durable inphysiological fluids, have been identified in which the fibercompositions contain silica (SiO₂), magnesia (MgO), and at least onecompound containing lanthanum or a lanthanide series element.

In certain embodiments, the fiber is manufactured from a melt ofingredients containing silica in an amount that is in the range of 71.25to about 86 weight percent, magnesia, and a lanthanide serieselement-containing compound.

There is provided a low shrinkage, refractory, vitreous inorganic fiberbased on a magnesium-silicate system having a use temperature up to atleast 1000° C., which maintains mechanical integrity after exposure tothe use temperature and which is non-durable in physiological fluids,such as lung fluid.

The non-durable refractory vitreous inorganic fiber, according to oneembodiment, comprises the fiberization product of about 71.25 to about86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound containing a lanthanide series element. The lanthanide serieselement-containing compound may be, for example, a oxide of a lanthanideseries element.

The non-durable refractory vitreous inorganic fiber, according to oneembodiment, comprises the fiberization product of about 71.25 to about86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound, such as an oxide, containing a lanthanide series element and,optionally, zirconia. If zirconia is included in the fiberization melt,then it is included in an amount generally in the range of greater than0 to about 11 weight percent.

According to a further embodiment, the non-durable refractory vitreousinorganic fiber comprises the fiberization product of about 71.25 toabout 86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound containing a lanthanide series element, and less than about 1weight percent iron oxide impurity, calculated as Fe₂O₃. The lanthanideseries element-containing compound may be, for example, a oxide of alanthanide series element.

The high temperature resistant, non-durable fibers, according to certainembodiments, preferably contain less than about 2 weight percent alumina(Al₂O₃).

A process is provided for the production of high temperature resistantvitreous inorganic fiber having a use temperature up to at least 1000°C., which maintains mechanical integrity up to the service temperatureand which is non-durable in physiological fluids comprising:

forming a melt with the ingredients comprising from about 71.25 to about86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound containing lanthanum or a lanthanide series element, andproducing fibers from the melt.

A process is further provided for the production of high temperatureresistant vitreous inorganic fiber having a use temperature up to atleast 1000° C., which maintains mechanical integrity up to the servicetemperature and which is non-durable in physiological fluids comprising:

forming a melt with ingredients comprising about 71.25 to about 86weight percent silica, about 14 to about 28.75 weight percent magnesia,and about greater than 0 to about 6 weight percent of a compoundcontaining lanthanum or a lanthanide series element, and, optionally,zirconia; and producing fibers from the melt.

The melt compositions utilized to produce the fibers of the presentinvention provide a melt viscosity suitable for blowing or spinningfiber, and for imparting mechanical strength for exposure to servicetemperature.

A method is further provided for insulating an article, includingdisposing on, in, near or around the article, a thermal insulationmaterial having a service temperature up to at least 1000° C., orgreater, which maintains mechanical integrity up to the use temperatureand which is non-durable in physiological fluids, said insulationmaterial comprising the fiberization product of a fiber melt comprisingsilica, magnesia, a compound containing lanthanum or a lanthanide serieselement and, optionally, zirconia.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a viscosity vs. temperature curve of a melt chemistry for acommercially available, spun aluminosilicate fiber.

FIG. 1B is a viscosity vs. temperature curve of a melt chemistry for acommercially available, blown aluminosilicate fiber.

DETAILED DESCRIPTION

There is provided a high temperature resistant fiber useful as a heat,electrical, sound insulation material, which has a temperature use limitgreater than 1000° C., and which is non-durable in physiological fluids,such as lung fluid. By non-durable in physiological fluids is meant thatthe fiber at least partially dissolves in such fluids (such as simulatedlung fluid) during in vitro tests.

In order for a glass composition to be a viable candidate for producinga satisfactory high temperature refractory fiber product, the fiber tobe produced must be manufacturable, sufficiently soluble inphysiological fluids, and capable of surviving high temperatures withminimal shrinkage and minimal loss of mechanical integrity duringexposure to the high service temperatures.

“Viscosity” refers to the ability of a glass melt to resist flow orshear stress. The viscosity-temperature relationship is critical indetermining whether it is possible to fiberize a given glasscomposition. An optimum viscosity curve would have a low viscosity (5-50poise) at the fiberization temperature and would gradually increase asthe temperature decreased. If the melt is not sufficiently viscous (ie.too thin) at the fiberization temperature, the result is a short, thinfiber, with a high proportion of unfiberized material (shot). If themelt is too viscous at the fiberization temperature, the resulting fiberwill be extremely coarse (high diameter) and short.

Viscosity is dependent upon melt chemistry, which is also affected byelements or compounds that act as viscosity modifiers. We have found forthis fiber chemistry system, the lanthanide element containing compoundacts as viscosity modifier which permit fibers to be blown or spun fromthe fiber melt. It is necessary, however, according to the presentinvention, that such viscosity modifiers, either by type or amount, donot adversely impact the solubility, shrink resistance, or mechanicalstrength of the blown or spun fiber.

Mechanical integrity is also an important property, since fiber mustsupport its own weight in any application and must also be able toresist abrasion due to moving air or gas. Indications of fiber integrityand mechanical strength are provided by visual and tactile observations,as well as mechanical measurement of these properties of after-servicetemperature exposed fibers.

The fiber has a compressive strength within a target range comparable tothat of a standard, commercial aluminosilicate fiber, and additionallyhas high compression recovery, or resiliency.

The fibers of the present invention are significantly less durable thannormal refractory ceramic fiber, such as aluminosilicates (about 50/50weight percent) and alumino-zirconia-silicates or AZS (about 30/16/54weight percent) in simulated lung fluid.

The non-durable refractory vitreous fibers are made by standard glassand ceramic fiber manufacturing methods. Raw materials, such as silica,any suitable source of magnesia such as enstatite, forsterite, magnesia,magnesite, calcined magnesite, magnesium zirconate, periclase, steatite,or talc, and, if zirconia is included in the fiber melt, any suitablesource of zirconia such as baddeleyite, magnesium zirconate, zircon orzirconia, are delivered in selected proportions from storage bins to afurnace where they are melted and blown using a fiberization nozzle, orspun, either in a batch or a continuous mode.

The viscosity of the melt may optionally be controlled by the presenceof viscosity modifiers, sufficient to provide the fiberization requiredfor the desired applications. The viscosity modifiers may be present inthe raw materials which supply the main components of the melt, or may,at least in part, be separately added. Desired particle size of the rawmaterials is determined by furnacing conditions, including furnace size(SEF), pour rate, melt temperature, residence time, and the like.

A compound containing a lanthanide series element can be effectivelyutilized to enhance the viscosity of a fiber melt containing silica andmagnesia as major components, thereby enhancing the fiberizability ofthe fiber melt. The use of the lanthanide element-containing compoundenhances viscosity and improves fiberization without adversely impactingthe thermal performance, mechanical properties, or solubility of thefiber product.

According to one embodiment, the refractory vitreous inorganic fiber iscapable of withstanding a use temperature of at least up to 1000° C.with less than about 6% linear shrinkage, preferably less than about 5%linear shrinkage, exhibits mechanical integrity at the servicetemperature, and is non-durable in physiological fluids, such as lungfluid. The non-durable refractory vitreous inorganic fiber comprises thefiberization product of about 71.25 to about 86 weight percent silica,about 14 to about 28.75 weight percent magnesia, and about greater than0 to about 6 weight percent of a compound containing lanthanum or alanthanide series element. The fiberization melt from which the fiberproduct is manufactured may also include from 0 to about 11 weightpercent zirconia.

The fiber should contain not more than about 1 weight percent calciaimpurity. According to other embodiments, the fiber should not containmore than about 1 weight percent iron oxides impurity (calculated asFe₂O₃). Other elements or compounds may be utilized as viscositymodifiers which, when added to the melt, affect the melt viscosity so asto approximate the profile, or shape, of the viscosity/temperature curveof a melt that is readily fiberizable, as discussed below.

Useful lanthanide series elements include La, Ce, Pr, Nd, Pm, Sm, Eu,Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and mixtures thereof. The element Yresembles many of the lanthanide series elements and is found with themin nature. For purposes of this specification, the element Y is to beconsidered to be included in the lanthanide series elements. In acertain embodiment, compounds containing the lanthanides elements La,Ce, Pr, Nd or combinations thereof can be added to the fiber melt. Aparticularly useful lanthanide series element that can be added to thefiber melt is La.

The compound containing a lanthanide series element may include, withoutlimitation, lanthanide series element-containing bromides, lanthanideseries element-containing chlorides, lanthanide serieselement-containing fluorides, lanthanide series element-containingphosphates, lanthanide series element-containing nitrates, lanthanideseries element-containing nitrites, lanthanide series element-containingoxides, and lanthanide series element-containing sulfates.

The oxides of the lanthanide series elements are useful for enhancingthe viscosity of a fiber melt containing silica and magnesia to enhancethe fiberizability of the melt. A particularly useful oxide of alanthanide series element is La₂O₃. La₂O₃ is commonly referred to in thechemical arts as “lanthanum” or “lanthanum oxide” and, therefore, theseterms may be used interchangeably in the specification.

As described above, mixtures of lanthanide series element-containingcompounds can be used in the fiber melt to enhance melt viscosity.Chemically, the lanthanide series elements are very similar and tend tobe found together in ore deposits. The term “misch metal” is used todesignate a naturally occurring mixture of lanthanide series elements.Further refining is required to separate and convert the misch metaloxide into its constituent misch metal oxides. Thus, misch metal oxideitself may be used as the lanthanide series element-containing compoundin the fiber melt.

While alumina is a viscosity modifier, the inclusion of alumina in thefiber melt chemistry results in a reduction in the solubility of theresulting fiber in physiological saline solutions. It is, therefore,desirable to limit the amount of alumina present in the fiber meltchemistry to at least below about 2 weight percent, and, if possible,with raw materials used, to less than about 1 weight percent.

One approach to testing whether a fiber of a defined composition can bereadily manufactured at an acceptable quality level is to determinewhether the viscosity curve of the experimental chemistry matches thatof a known product which can be easily fiberized. The addition oflanthanum oxide to a magnesium-silicate melt enhances fiberization byextending the viscosity curve of the melt to lower temperatures and highviscosities. As the lanthanum-silicate system is a more refractorysystem than the magnesium-silicate system, thermal performance of theresulting fiber is also enhanced.

The shape of the viscosity vs. temperature curve for a glass compositionis representative of the ease with which a melt will fiberize and thus,of the quality of the resulting fiber (affecting, for example, thefiber's shot content, fiber diameter, and fiber length). Glassesgenerally have low viscosity at high temperatures. As temperaturedecreases, the viscosity increases. The value of the viscosity at agiven temperature will vary as a function of composition, as will theoverall steepness of the viscosity vs. temperature curve. The viscositycurve of melt of silica, magnesia, and lanthanum or other lanthanideseries element-containing compound has a viscosity that approximates thetarget viscosity curve of FIG. 1A for the commercially available, spunaluminosilicate fiber.

The fiber comprises the fiberization product of about 65 and about 86weight percent silica, about 14 to about 35 weight percent magnesia, anda lanthanide series element-containing compound.

The non-durable refractory vitreous inorganic fiber, according to acertain embodiment, comprises the fiberization product of about 71.25 toabout 86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound containing lanthanum or a lanthanide series element.

According to other embodiments, the non-durable, high temperatureresistant vitreous inorganic fiber comprises the fiberization product ofabout 71.25 to about 86 weight percent silica, about 14 to about 28.75weight percent magnesia, and about greater than 0 to about 6 weightpercent of a compound containing lanthanum or a lanthanide serieselement, 0 to about 11 weight percent zirconia, and less than about 2weight percent alumina.

In the melt and fibers discussed above, an operable silica level isbetween about 71.25 and about 86 weight percent, preferably betweenabout 72 and about 80 weight percent, with the upper level of silicalimited only by manufacturability of the fiber.

According to another embodiment, the non-durable, high temperatureresistant vitreous inorganic fiber comprises the fiberization product ofabout 72 to about 80 weight percent silica, about 21 to about 28 weightpercent magnesia, and from greater than 0 to about 6 of a lanthanideseries element-containing compound. Of course, the sum of the amountsilica, magnesia and lanthanide series element-containing compound, inweight percent, cannot exceed 100 weight percent.

According to a further embodiment, the non-durable refractory vitreousinorganic fiber comprises the fiberization product of about 71.25 toabout 86 weight percent silica, about 14 to about 28.75 weight percentmagnesia, and about greater than 0 to about 6 weight percent of acompound containing a lanthanide series element, wherein the fibercontains substantially no alkali metal oxide.

The fibers contain substantially no alkali metal, greater than traceimpurities. The term “trace impurities” refers to those amounts of asubstance in the fiberization product that are not intentionally addedto the fiber melt, but which may be present in the raw startingmaterials from which the fibers are produced. Thus, the phrase“substantially no alkali metal oxide” means that the alkali metal oxide,if present in the fiber, is from the raw starting materials and thealkali metal oxide was not intentionally added to the fiber melt.Generally, the fibers may contain alkali metal oxide from the startingraw materials in amounts up to about tenths of a percent, by weight.Thus, the alkali metal content of these fibers is generally in the rangeof trace impurities, or tenths of a percent at most, calculated asalkali metal oxide. Other impurities may include iron oxides, in theamount of less than about 1 weight percent, calculated as Fe₂O₃, or aslow as possible.

The non-durable, low shrinkage, vitreous inorganic fibers describd abovecompare favorably with conventional kaolin, AZS, and aluminosilicatedurable refractory ceramic fibers in terms of mechanical strength up toservice temperature.

The fibers are manufactured from a melt of ingredients containingsilica, magnesia, a lanthanide series element-containing compound and,optionally, zirconia by known fiber spinning or blowing processes. Thefibers may have fiber diameters that are only practical upper limit forfiber diameter is the ability to spin or blow product having the desireddiameter.

The fiber may be manufactured with existing fiberization technology andformed into multiple product forms, including but not limited to bulkfibers, fiber-containing blankets, papers, felts, vacuum cast shapes andcomposites. The fiber may be used in combination with conventionalmaterials utilized in the production of fiber-containing blankets,vacuum cast shapes and composites, as a substitute for conventionalrefractory ceramic fibers. The fiber may be used alone or in combinationwith other materials, such as binders and the like, in the production offiber-containing paper and felt. The fiber is soluble in the simulatedphysiological lung fluid, thus minimizing concerns over fiberinhalation.

A method of insulating an article with thermal insulation material isalso provided. According to the method of thermally insulating anarticle, thermal insulation material having a service temperature up toat least 1000° C. or greater, which maintains mechanical integrity up tothe use temperature, and which is non-durable in physiological fluids,is disposed on, in, near or around the article to be insulated. Thethermal insulation material utilized in the method of thermallyinsulating an article comprises the fiberization product of a melt ofingredients comprising silica, magnesia, a compound containing lanthanumor a lanthanide series element and, optionally, zirconia.

The high temperature resistant refractory glass fibers are readilymanufacturable from a melt having a viscosity suitable for blowing orspinning fiber, and are non-durable in physiological fluids areprovided.

The high temperature resistant refractory glass fibers are non-durablein physiological fluids, and exhibit good mechanical strength up to theservice temperature.

The high temperature resistant refractory glass fibers are non-durablein physiological fluids, and exhibit low shrinkage at the usetemperature.

EXAMPLE

Fibers were produced from a melt of ingredients containing silica,magnesia, and 1 weight percent La₂O₃ by a fiber blowing process. Theshrinkage characteristics of the fibers were tested by wet formingfibers into a pad and measuring the dimensions of the pad before andafter heating the shrinkage pad in a furnace for a fixed period of time.

A shrinkage pad was prepared by mixing the blown fibers, a phenolicbinder, and water. The mixture of fiber, binder, and water was pouredinto a sheet mold and the water was allowed to drain through the bottomof the mold. A 3 inch×5 inch piece was cut from the pad and was used inthe shrinkage testing. The length and width of the test pad wascarefully measured. The pad was then placed into a furnace and broughtto a temperature of 1260° C. for 24 hours. After heating for 24 hours,the pad was cooled and the length and width were measured again. Thelinear shrinkage of the test pad was determined by comparing the“before” and “after” dimensional measurements. The test pad, comprisingfibers prepared in accordance with the present invention, exhibited alinear shrinkage of about 4% or less.

The present invention is not limited to the specific embodimentsdescribed above, but includes variations, modifications and equivalentembodiments. The embodiments that are disclosed separately are notnecessarily in the alternative, as various embodiments of the inventionmay be combined to provide the desired characteristics.

1. A low shrinkage, high temperature resistant vitreous inorganic fiberhaving a use temperature up to at least 1000° C. or greater, whichmaintains mechanical integrity up to the use temperature and which isnon-durable in physiological fluids, comprising the fiberization productof greater than 71.25 weight percent silica, magnesia, and a lanthanideseries element-containing compound.
 2. The fiber of claim 1, whereinsaid lanthanide series element is selected from the group consisting ofLa, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
 3. Thefiber of claim 2, wherein said lanthanide series element is La.
 4. Thefiber of claim 1, wherein said lanthanide series element-containingcompound is selected from the group consisting of lanthanide serieselement-containing bromides, lanthanide series element-containingchlorides, lanthanide series element-containing fluorides, lanthanideseries element-containing phosphates, lanthanide serieselement-containing nitrates, lanthanide series element-containingnitrites, lanthanide series element-containing oxides, and lanthanideseries element-containing sulfates.
 5. The fiber of claim 4, whereinsaid lanthanide series element-containing compound is La₂O₃.
 6. Thefiber of claim 1, further comprising from 0 to about 11 weight percentzirconia.
 7. The fiber of claim 1, containing less than about 2 weightpercent alumina.
 8. The fiber of claim 1, containing less than about 1weight percent iron oxide, calculated as Fe₂O₃.
 9. The fiber of claim 1,containing substantially no alkali metal oxide.
 10. The fiber of claim1, containing less than about 1 weight percent calcia.
 11. The fiber ofclaim 1, comprising the fiberization product of greater than 71.25 toabout 86 weight percent silica, about 14 to about 35 weight percentmagnesia, and greater than 0 to about 6 weight percent of a lanthanideseries element-containing compound.
 12. The fiber of claim 11, whereinsaid lanthanide series element is selected from the group consisting ofLa, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
 13. Thefiber of claim 12, wherein said lanthanide series element is La.
 14. Thefiber of claim 11, wherein said lanthanide series element-containingcompound is selected from the group consisting of lanthanide serieselement-containing bromides, lanthanide series element-containingchlorides, lanthanide series element-containing fluorides, lanthanideseries element-containing phosphates, lanthanide serieselement-containing nitrates, lanthanide series element-containingnitrites, lanthanide series element-containing oxides, and lanthanideseries element-containing sulfates.
 15. The fiber of claim 14, whereinsaid lanthanide series element-containing compound is La₂O₃.
 16. Thefiber of claim 11, further comprising from 0 to about 11 weight percentzirconia.
 17. The fiber of claim 11, containing less than about 2 weightpercent alumina.
 18. The fiber of claim 11, containing less than about 1weight percent iron oxide, calculated as Fe₂O₃.
 19. The fiber of claim11, containing substantially no alkali metal oxide.
 20. The fiber ofclaim 11, containing less than about 1 weight percent calcia.
 21. Thefiber of claim 1, comprising the fiberization product of greater than71.25 to about 86 weight percent silica, about 14 to about 28.75 weightpercent magnesia, and greater than 0 to about 6 weight percent of alanthanide series element-containing compound.
 22. The fiber of claim21, wherein said lanthanide series element is selected from the groupconsisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu.
 23. The fiber of claim 22, wherein said lanthanide seriesclement is La.
 24. The fiber of claim 21, wherein said lanthanide serieselement-containing compound is selected from the group consisting oflanthanide series element-containing bromides, lanthanide serieselement-containing chlorides, lanthanide series element-containingfluorides, lanthanide series element-containing phosphates, lanthanideseries element-containing nitrates, lanthanide series element-containingnitrites, lanthanide series element-containing oxides, and lanthanideseries element-containing sulfates.
 25. The fiber of claim 24, whereinsaid lanthanide series element-containing compound is La₂O₃.
 26. Thefiber of claim 21, further comprising from 0 to about 11 weight percentzirconia.
 27. The fiber of claim 21, containing less than about 2 weightpercent alumina.
 28. The fiber of claim 21, containing less than about 1weight percent iron oxide, calculated as Fe₂O₃.
 29. The fiber of claim21, containing substantially no alkali metal oxide.
 30. The fiber ofclaim 21, containing less than about 1 weight percent calcia.
 31. Thefiber of claim 21, comprising fiberization product of about 72 to about79 weight percent silica, about 21 to about 28 weight percent magnesia,and greater than 0 to about 6 weight percent of a lanthanide serieselement-containing compound.
 32. The fiber of claim 31, wherein saidlanthanide series element is selected from the group consisting of La,Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.
 33. Thefiber of claim 32, wherein said lanthanide series element is La.
 34. Thefiber of claim 31, wherein said lanthanide series element-containingcompound is selected from the group consisting of lanthanide serieselement-containing bromides, lanthanide series element-containingchlorides, lanthanide series element-containing fluorides, lanthanideseries element-containing phosphates, lanthanide serieselement-containing nitrates, lanthanide series element-containingnitrites, lanthanide series element-containing oxides, and lanthanideseries element-containing sulfates.
 35. The fiber of claim 34, whereinsaid lanthanide series element-containing compound is La₂O₃.
 36. Thefiber of claim 31, further comprising from 0 to about 11 weight percentzirconia.
 37. The fiber of claim 31, containing less than about 2 weightpercent alumina.
 38. The fiber of claim 31, containing less than about 1weight percent iron oxide, calculated as Fe₂O₃.
 39. The fiber of claim31, containing substantially no alkali metal oxide.
 40. The fiber ofclaim 31, containing less than about 1 weight percent calcia.
 41. Amethod for preparing a low shrinkage, high temperature resistantvitreous fiber having a use temperature up to at least 1000° C. orgreater, which maintains mechanical integrity up to the use temperatureand which is non-durable in physiological fluids, comprising forming amelt with ingredients comprising greater than 71.25 weight percentsilica, magnesia, and a lanthanide series element-containing compound;and producing fibers from the melt.
 42. The method of claim 41, whereinthe melt comprises from greater than 71.25 to about 86 weight percentsilica, about 14 to about 35 weight percent magnesia, and greater than 0to about 6 weight percent of a lanthanide series element-containingcompound.
 43. The method of claim 41, wherein the melt comprises fromabout 71.25 to about 86 weight percent silica, about 14 to about 28.75weight percent magnesia, and greater than 0 to about 6 weight percent ofa lanthanide series element-containing compound.
 44. The method of claim43, wherein the melt comprises from about 72 to about 79 weight percentsilica, about 21 to about 28 weight percent magnesia, and greater than 0to about 6 weight percent of a lanthanide series element-containingcompound.
 45. The method of claim 41, wherein said lanthanide serieselement is selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm,Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.
 46. The method of claim 45,wherein said lanthanide series element is La.
 47. The method of claim41, wherein said lanthanide series element-containing compound isselected from the group consisting of lanthanide serieselement-containing bromides, lanthanide series element-containingchlorides, lanthanide series element-containing fluorides, lanthanideseries element-containing phosphates, lanthanide serieselement-containing nitrates, lanthanide series element-containingnitrites, lanthanide series element-containing oxides, and lanthanideseries element-containing sulfates.
 48. The method of claim 47, whereinsaid lanthanide series element-containing compound is La₂O₃.
 49. Themethod of claim 41, further comprising from 0 to about 11 weight percentzirconia.
 50. The method of claim 41, containing less than about 2weight percent alumina.
 51. The method of claim 41, containing less thanabout 1 weight percent iron oxide, calculated as Fe₂O₃.
 52. The methodof claim 41, containing substantially no alkali metal oxide.
 53. Themethod of claim 41, containing less than about 1 weight percent calcia.54. A method of insulating an article, including disposing on, in, nearor around the article, a thermal insulation material having a servicetemperature up to at least 1000° C., or greater, which maintainsmechanical integrity up to the use temperature and which is non-durablein physiological fluids, said insulation material comprising thefiberization product of a melt of ingredients comprising greater than71.25 weight percent silica, magnesia, a compound containing lanthanumor a lanthanide series element and, optionally, zirconia.